[quote]Originally posted by Outsider:
<strong>I understand the concept of light cones also; it's one of the reasons why we cannot travel faster than light in this universe. Imagine a person in a spaceship that can travel 4 times the speed of light. He is in orbit around a star 8 light years away. He has a missile that can destroy the star and he launches it to cause the collapse of the star. He then travels to earth at top speed (this takes him 2 years) and predicts the destruction of that star. If all goes well, in 6 years the star will explode in a fireshow that will be visable from earth because it take light 8 years to transverse the 8 light years minus the time it took him to get to earth. But lets say someone doesn't like the idea of this joker taking out a star for his own glory, so he hops in his Super Cruiser10 (that can travel 10 times the speed of light) and he gets there just before the first guy is about to destroy the star. So he blasts him to smithereens. So whats the problem? The problem is this second guy basically MADE his own light cone. They both did in fact. The first guy made a light cone by going to earth before earth's light cone showed the destruction of the star. he had knowledge that he should not have had; prediction of a future event. It's not like predicting weather either; it was a cosmilogical change induced by his actions. The second guy compounded it by nullifying the first light cone and introducing a new cone. But the star WAS destroyed. But because he interveened that effect was nullified in the universe. Just imagine the implications, just by travelling faster than light you force the immediate vicinity of that part of the universe to go BACK in time while the rest of the universe continues on it's own timeline! This would require infinate energy to acomplish. That's why faster than light travel is impossible and light cones cannot be tampered with.</strong><hr></blockquote>
To me, this isn't making a damn bit of sense. Okay, SpaceMan1 decides to go to Star1, blows it to hell, travels 8 lightyears back to Earth at 8x lightspeed in two years, predicts the explosion of Star1, six years later, it happens. Gotcha.
But SpaceMan2, when does he leave, when SpaceMan1 comes to earth and predicts it, 1/10 of a year before SpaceMan1 decides to blow up the star, or when the light of the star blowing up reaches Earth?
If it was the latter, and SpaceMan2 travels to Star1 at 10x lightspeed, logic tells me he will see the star 1/10 of a year after it was blown up by SpaceMan1. SpaceMan1 will have departed 6.1 years ago. On the other hand, SpaceMan2 will be looking at Earth and will see it eight years in the past.
So how is it that SpaceMan2 kills SpaceMan1 again?
Now, if he left at the time that SpaceMan1 predicted the explosion, logic tells me that he would intercept the light given off when the star exploded 5.4545 lightyears away from Earth, then start passing through the light image, which would appear at an accelerated rate, only to arrive at Star1 2.1 years after Star1 Exploded.
<img src="confused.gif" border="0">
[ 12-01-2002: Message edited by: Spart ]</p>